The present invention relates to organic semiconductor components and to the production thereof.
In the field of organic semiconductors, it is known that electron transport layers have to be used for transport of electrons as charge carriers, and hole transport layers for transport of holes as charge carriers.
An organic light-emitting diode is just one example from the related art in which doping is used to increase the conductivity of charge transport layers and charge generation layers. In organic field-effect transistors, solar cells or photodetectors too, the problem of doping arises, for example for injection layers to reduce the contact resistance, for example at source and drain electrodes, or electrodes in general.
An example of a procedure known in principle for the doping of organic materials is to introduce dopant molecules or dopant ions into a matrix of an organic substance. For the p-doping of hole conductor layers, electron acceptors are introduced. Known examples of such electron acceptors suitable for p-doping are metal complexes. The already known dopants used usually have disadvantages either in the processing or else in the effect thereof on properties of the semiconductor component outside the area of increased conductivity. Such areas are, for example efficiency and lifetime. In most organic semiconductor components, efficiency and lifetime depend strongly on the charge carrier density at various interfaces. Especially in organic light-emitting diodes, the exciton density in the light-emitting layer determines the light yield and efficiency of the component.
With regard to the processing of the dopants for production of the component, the problem frequently exists in the related art that the dopants are restricted to one deposition method and accordingly can be processed exclusively from the gas phase or exclusively from the liquid phase. Accordingly, these dopant classes are also each restricted to one material class for the semiconductor matrix. In other words, a dopant which can be deposited only from the liquid phase can only be introduced into a polymer matrix. A dopant which can be deposited exclusively from the gas phase can only be introduced into a small molecule matrix. In the case of suitability for deposition from the gas phase, an additional factor is that the dopant has to be heatable to a certain temperature without decomposing. Only when the dopant is suitable for forming a doped hole conductor layer together with the matrix material in a condensation reaction is it an option for use in component production.
As well as these additional demands on dopants, the primary aim is to further improve the doping action thereof and thus to further increase the conductivity of organic semiconductor layers.